Hydraulic continuously variable transmissions which comprise a swash plate type hydraulic pump and a hydraulic motor have been known. For example, Japanese Laid-Open Patent Publications No. H7(1995)-280063 and No. H8(1996)-74965 disclose such transmissions. The transmission disclosed in Japanese Laid-Open Patent Publication No. H7(1995)-280063 is a hydrostatic transmission which comprises a hydraulic pump with a variable swash plate and a hydraulic motor with a fixed swash plate. In this transmission, the hydraulic pump, which is driven by the engine to supply oil to the hydraulic motor for actuation, is connected with the hydraulic motor through a hydraulic closed circuit. In this construction, the hydraulic pump, the hydraulic closed circuit and the hydraulic motor are connected in series in this respective order.
On the other hand, the transmission disclosed in Japanese Laid-Open Patent Publication No. H8(1996)-74965 is a hydromechanical transmission which comprises a hydraulic pump with a variable swash plate, a hydraulic motor with a fixed swash plate, and a power distribution mechanism, which divides the output of the engine into two portions, one to drive the hydraulic pump and the other to drive the output shaft of the transmission. Here, the hydraulic pump driven by the engine supplies oil through a hydraulic closed circuit to the hydraulic motor for the actuation of the motor. In this construction, the hydraulic closed circuit is arranged or formed in a control block, and the hydraulic pump and the hydraulic motor are positioned on this control block above and below the control block.
In any FR drive vehicle, naturally, the engine is placed in the front part of the vehicle, and the output shaft of the engine is connected through a transmission to a propeller shaft, which extends rearward through the central lower portion of the vehicle body. In this power transmission system, the rotational drive power of the engine taken out through the output shaft thereof is transmitted to the rear wheels of the vehicle through the propeller shaft. Generally, the transmission is provided at the rear end of the engine, extending rearward, so the drive power, which is received from the engine through the engine output shaft, is transmitted to the propeller shaft through the transmission, which changes the speed ratio. In the construction of this type of power transmission system, which is designed for FR drive vehicles, it is typical that the unit which includes the transmission and the propeller shaft is placed inside a floor tunnel which extends from the front part of the vehicle to the rear part in the cabin.
It is generally desired that the cabin space, i.e., the accommodation space available for the driver and other people riding the vehicle, be made as wide as possible to provide comfort. Also, there is a desire to improve the degree of freedom in laying out the cabin. Therefore, there is need to minimize the floor tunnel which protrudes or rises into the cabin, and there is a desire to form the floor tunnel in a straight line without ups and downs. Thus, the transmission, which is placed in the floor tunnel, is now required to have a configuration that can satisfy such need and desire.